Torsion balance



Ami-1213,1970 GRAN 3,508,624

TORSION BALANCE Filed April 1, 1968 I5 Sheets-Sheet 1 INVENTOR:

Knm. HORA n A ifs/m n 3 Sheets-Sheet 2 Filed April 1, 1968 INVENTOR;

mu Roan BY W14 HTI' IINEILS United States Patent US. Cl. 177-178 15 Claims ABSTRACT OF THE DISCLOSURE Torsion balance includes a fixed middle truss carrying upper and lower bands, and a pair of parallel beams supported on the bands. An end truss carrying upper and lower bands is mounted by means of the bands between the beams at each end of the latter. Both beams and the end trusses they carry can pivot about the bands of the middle truss by twisting the latter. Balance carries an indicator including a vane arranged to partially obstruct a beam of light, image of vane being projected on a fixed graduated screen. Means provide to adjust effective length of one arm of each beam.

This invention relates to torsion balances.

The object of the present invention is to provide an improved torsion balance.

According to the present invention, there is provided a torsion balance having a base and a framework, said framework including a middle truss rigidly mounted on said base and having truss bands, 21 pair of beams mounted on the middle truss bands for rotation about said bands as fulcrum points and two ends trusses, each having truss bands attached to the respective end regions of the arms of said beams, there being means providing adjustment of the effective length of one of said arms of each beam, said adjustment being available on one side of said middle truss bands, further means being provided which are operative to indicate, in terms of weight, rotational movement of said beams about said fulcrum points, said indicating means including a vane connected to said framework and arranged to pass through a beam of light thus casting an image, which, by means of an optical device, is

. arranged to pass unobstructed through the area defined by the framework thereafter to be projected onto a graduated screen.

The invention will now be described further, by way of example only, with reference to one practical form thereof, as illustrated in the accompanying drawings in which:

FIG. 1 is a side elevation of a torsion balance to be described, parts being omitted for clarity,

FIG. 2 is a perspective view of the arrangement shown in FIG. 1, but with most of said parts included,

FIG. 3 is a side elevation of the arrangement of FIG. 1 and including the parts illustrated in FIG. 2,

FIG. 4 is an elevation of one end of the arrangement of FIGS. 1 to 3, and

FIG. 5 is an elevation from the other end.

In a torsion balance, made in accordance with the present invention, there is provided a base on which is mounted a framework. The framework comprises a middle truss 11 mounted on the base 10 and two end trusses 12 and 13.

Each truss is substantially rectangular in form and ha recessed channel portions 14 at the top and bottom thereof. In the centre of each truss is a rectangular aperture 10a. Each truss effectively has top and bottom truss bands extending across the recessed portions 14, these bands being numbered 11a and 11b; 12a and 12b, and 13a and 13b, respectively. The truss bands are of flexible steel or other suitable material and each is conveniently formed 3,508,624 Patented Apr. 28, 1970 as a continuous flexible strip wrapped tightly around the periphery of each truss. They are held in position by retaining plates 15, secured to the trusses and are kept taut by tension adjusters 16.

,There are provided upper and lower beams 17 and 18 having middle and end region attachment plates 19, 20 and 21 screwed to the beams 17 and 18. The attachment plates 19, 20 and 21 are adapted to attach the beams 17 and 18 to the truss bands 11a, 1111, etc. One end region attachment plate 20 of each beam 17, 18 is adjustable slightly in a direction parallel to the longitudinal axis of the beam.

- The framework is assembled with the middle truss 11 mounted on the base 10 by mounting brackets 10b, the middle truss bands 11a, and 11b supporting the beams 17 and 18 by means of their middle attachment plates 19 and the end regions of the beams 17 and 18 supporting the end truss bands 12a, 12b and 13a, 13b and thus the end trusses 12 and 13. Thus the assembly is rotatable about the fulcrum point provided by the middle truss bands 11a and 11b, one end truss 12 being adjustable in position relative to the middle truss 11 and the other end truss 13.

Mounted on one end of one'of the beams is a rigid vane assembly. The vane assembly consists of a centre beam 22 connected, by a flexible strip 23, to the end of the upper beam 17 adjacent the truss 13. The beam 22 is pivoted about a further flexible band 24 stretched between portions of a split supporting beam 25. Each part of the beam 25 is mounted on one of two screen-supporting pillars 26, to be described. The beam 22 thus extends from outside of the end truss 13, through the framework (i.e. the apertures 10a in the trusses) and emerges at a position outside of the end truss 12 where it is arranged to support an angled member 27, to which is attached an.indicator vane 28. The latter is arranged to pass through a beam of light transmitted from a lamp 29 to a lens system 30. This is in the form of a zoom lens, whose purpose will be described hereinafter.

The vane 28 passing through the beam of light casts an image which is projected by the zoom lens 30 onto a first mirror 31, mounted adjacent the latter and thereafter onto a second mirror 32 mounted adjacent the first. From the second mirror 32, the image is projected through the framework of trusses to the other end of the apparatus where a third mirror 33 is mounted. The mirror 33 projects the image upwardly onto a graduated screen 34 mounted between the screen-supporting pillars 26 and preferably graduated to have a centre zero reading. The path of light is illustrated diagrammatically in FIG. 1.

The apparatus so far described is conveniently located in a housing (not shown) in which the graduated screen 34 is visible. Support means (not shown) are attached to the end truss 12 and are arranged to support a weighing pan or platform (also not shown), for articles to be weighed. Means are associated with the other end truss 13 such that, when required, the latter can be subjected to a standard load.

For example, if the torsion balance is adapted for use in checking the weight of packets of biscuits labelled 1 1b., then a load of one pound (or its equivalent) is applied to the end truss 13, so that the weight of the unknown article can be checked by placing it on the weighing pan attached to the end truss 12. Clearly the arrangement can be such that a plurality of standard weights could be selectively applied to the truss 13 so that the apparatus I as a coil spring. The other end of the spring 36 is rigidly attached to a boss 37 being part of a pinion 38 mounted for rotation on the base 10. Meshing with the pinion 38 is a worm wheel 39 also mounted for rotation on the base 10. The shaft 40 of the worm wheel 39 is formed as one part of a dog clutch 41, the other half of which is rotatably and slidably mounted on the base and is adapted to receive an operating knob (not shown). The tare adjustment device is adapted, by rotation of the pinion 38, to increase or reduce tension in the coil spring, which in turn causes the whole framework to rotate, one way or the other, about the fulcrum point until a zero reading is obtained.

In use therefore, when a load is applied to the balance as described previously with an appropriate counter-load in position, the framework oscillates until a point of equilibrium is reached. At this point the vane 28 is located in such a position as to give a reading on the screen 34. If the unknown article is equal to the standard weight, the reading is zero. The reading is indicated by comparison of light and shadow formed by the vane 28 passing through the beam of light. It will be appreciated that for a given oscillatory movement of the framework, there will be a greater movement of the vane 28 due to the arrangement of the beam 22 pivoting about the strip 24. In this manner an accurate reading is obtained.

When the apparatus has been assembled, the adjustable attachment plate on one end, the beams 17 and 18 are adjusted with the apparatus on load. This adjustment causes the effective length of one of the arms of each beam on one side of the middle truss to be adjusted, thereby to pre-set the balance under loaded conditions to counteract any discrepancy in balance caused by bowing of the truss bands or by slight manufacturing defects.

Further Working adjustments can be made Whenever necessary. These are the zero-setting tare adjustment referred to previously and the adjustment provided by the zoom lens. The latter is for correction of equal errors either side of zero and effectively causes the full image range to be increased or reduced in length. The variation is continuously variable, which provides fine adjustment.

Damping means (not shown) are provided which may be of any known type such as magnetic or hydraulic and limit stops 42 are adjustably mounted on the base 10 be low the end trusses 12 and 13.

The invention is not restricted to the details heretofore described. For example, the arrangement can be of the type having two Weighing pans exposed above the hous ing. In such an arrangement however, the space required to house a second weighing pan would cause the apparatus to be more cumbersome. This is a disadvantage which has been overcome to an appreciable extent by causing the beams of light to pass Within the framework rather than around the latter as in previously known balances.

What I claim is:

1. A torsion balance having a base and a framework, said framework including a middle truss rigidly mounted on said base and having truss bands, a pair of beams mounted on the middle truss bands for rotation about said bands as fulcrum points, and two end trusses, each having truss bands attached to the respective end regions of the arms of said beams, there being means providing adjustment of the effective length of one of said arms of each beam, said adjustment being available on one side of said middle truss bands, further means being provided which are operative to indicate, in terms of Weight, rotational movement of said beams about said fulcrum points, said indicating means including a vane connected to said framework and arranged to pass through a beam of light thus casting an image, which, by means of an optical device, is arranged to pass unobstructed through the area defined by the framework thereafter to be projected onto a graduated screen.

2. A torsion balance as claimed in claim 1, in Which said truss bands are mounted on said trusses in such a manner as to extend across recessed portions of the latter, each said truss having two recessed portions each of which is adapted effectively to receive one truss band.

3. A torsion balance as claimed in claim 2, in which the two truss bands effectively provided on each truss are formed as parts of a continuous flexible strip wrapped around the periphery of the truss.

4. A torsion balance as claimed in claim 1 in which each truss is substantially rectangular in form and is provided with a similarly shaped aperture therein, for the passage of light from the optical device.

5. A torsion balance as claimed in claim 1 in which the truss bands are attached to the trusses by retaining plates mounted on the latter and are kept taut by tension adjusters.

6. A torsion balance as claimed in claim 1 in which the beams are mounted across the top and bottom of the trusses and are attached to the truss bands by three attachment plates mounted on each beam, one end attachment plate of each beam being adjustable, longitudinally relative thereto, thus forming said adjustment means.

7. A torsion balance as claimed in claim 1 in which one end truss is arranged to be subjected to a standard load for comparison, and thus measurement, of the Weight of an object applied to the other end truss.

8. A torsion balance as claimed in claim 7, in which a plurality of standard loads are capable selectively of being applied to said first end truss.

9. A torsion balance as claimed in claim 1 in which there is provided tare adjustment means including a coil spring, one end of which is connected to said framework, the other end being attached to means adapted to adjust the tension of said coil spring thereby to cause said framework to rotate about the fulcrum point, whereby a zero setting can be attained.

10. A torsion balance as claimed in claim 9 in which said tension adjustment means includes a pinion, to Which is attached said end of said spring, said pinion meshing with a worm wheel adapted to be rotated, thereby to adjust the tension in said spring.

11. A torsion balance as claimed in claim 10, in which the shaft of said worm wheel is formed as one part of a dog clutch, the other half of which is rotatably and slidably mounted on the base and is adapated to receive an operating knob, whereby the tare adjustment means cannot be operated unless the clutch is engaged.

12. A torsion balance as claimed in claim 1, in which said vane is connected to said framework by means of a centre beam attached to one of said end trusses and mounted for rotation about a further flexible band as a fulcrum point, adjacent said end truss, said centre beam extending to a position adjacent said other end truss and supporting an angled member on which is mounted said vane.

13. A torsion balance as claimed in claim 12, in which said centre beam extends through the area defined by the framework.

14. A torsion balance as claimed in claim 1, in which said optical device includes a zoom lens.

15. A torsion balance as claimed in claim 1, in which the apparatus is enclosed within a housing, a weighing pan or platform being attached to one of the end trusses and extending through onto the exterior of the housing for receiving articles to be weighed.

References Cited UNITED STATES PATENTS 3,075,596 1/1963 Richardson 177-196 XR ROBERT S. WARD, 111., Primary Examiner US. Cl. X.R. 

